1. Field of the Invention
This invention relates to a lateral-type magnetically sensitive semiconductor device.
2, Description of the Prior Art
A magnetically sensitive semiconductor which detects the strength of a magnetic field by a difference current between two collector electrodes is known in the art. FIGS. 3A through 3C are diagrams illustrating the operating principle of an ordinary magnetically sensitive semiconductor. In the case illustrated, the carriers of the semiconductor are electrons (i.e., the semiconductor is an npn transistor), the equivalent circuit of which is shown in FIG. 3C. In general, a magnetically sensitive semiconductor has a specific sensitivity S expressed by .DELTA.I.sub.C /I.sub.CO .multidot..DELTA.B, where .DELTA.I.sub.C represents the difference current between two collectors, I.sub.CO the collector current when a magnetic field B=0, and .DELTA.B an amount of change in the magnetic field.
FIG. 3A illustrates a state in which the magnetic field B is not being applied. At such time the amounts of electrons which reach collectors C1, C2 from an emitter E are substantially equal, and therefore the collector currents are equal (IC.sub.1 =IC.sub.2). Accordingly, the difference current .DELTA.I.sub.C between the two collectors is zero. By contrast, FIG. 3B illustrates a state in which the magnetic field B is applied perpendicularly to the transistor. Here the direction of electron migration is curved as shown in the diagram owing to a Lorentz force produced by the magnetic field B, as a result of which the amount of electrons reaching the collector C1 is greater than that reaching the collector C2. In other words, the collector current IC.sub.1 becomes greater than the collector current IC.sub.2. Thus, the strength of the magnetic field B is obtained in accordance with B .varies..DELTA.I.sub.C (difference current)=IC.sub.1 -IC.sub.2 &gt; 0. By changing the potentials of the bases B, the field detection characteristic can be made linear and the collector current can be amplified.
In a magnetically sensitive semiconductor device having such a construction, it is desired that only carriers affected by the magnetic field be injected into the collectors. However, the magnetically sensitive semiconductor device having the conventional construction is such that carriers unnecessary for field detection also are injected into the two collectors Cl, C2, as a result of which accurate field detection cannot be carried out. In actuality, moreover, all of the carriers influenced by the magnetic field are not injected into the collectors Cl, C2; some flow out from both sides of the emitter. For this reason, the magnetic field cannot be measured accurately. Furthermore, it is required that the lengths of carrier migration (the distances from the emitter to the collectors) are made sufficiently large in order to detect the influence of the magnetic field. However, when these distances are lengthened, the number of carriers reaching the collectors diminishes and sensitivity declines.